The world's total human population has jumped to more than 7.4 billion just this year. Feeding the human species takes a tremendous toll on our natural resources including water, soil and phosphorus - a chemical element in fertilizer essential for food production. In modern agriculture, fertilizer often leaks into waterways such as rivers, lakes and oceans. The phosphorus (P) in the runoff stimulates algae blooms and then, when algae die and decompose, dead zones develop and fish die off. But much of the "lost" phosphorus doesn't end up in water bodies - large amounts of P also accumulate in the landscape. Until now, scientists have not had a good handle on the magnitude of this accumulation. [Source: Arizona State University]